Toby,
Don't have much in the way of advice but I really enjoyed reading your posts.
It sounds like he's a very lucky little quail to have you to take care of him!
It's amazing the bond you can develop with a special needs animal. I just lost my little Crissy (Easter Egger chicken with a crossed beak) a few months ago. She was about 18 months old. She got along pretty well with a few extra little modifications to the coop. (Deep water pan and wet mash mostly.) Her life was a bit of a struggle but she seemed happy out sun bathing, pecking around, etc. with the other "girls". Losing her was REALLY hard!
You might enjoy watching the following You Tube video even though this chick's situation is different than your quail's. I have seen it several times and get teary-eyed every time. Someone here at BYC posted a link to it years ago.
If the link doesn't work I think it's called "Don't kill that chick" (I think it used to be called "Saving Elvis"?
Treats?
A "chick stick" treat is similar to a flock block (mentioned above) only much smaller and it can be hung at the appropriate height so it doesn't get messed on.
A little bit of canned cat food might make a good treat? What do other people think?
My parents use to give their quails a little bit of salad greens and an occasional piece of strawberry.
Good luck with your little quail!